/ Dictionary / Index C caffeine: Meaning and Definition of Find definitions for: caf•feine Pronunciation: (ka-fēn', kaf'ēn, kaf'ē-in), [key] — n. Chem., Pharm. a white, crystalline, bitter alkaloid, CHNO, usually derived from coffee or tea: used in medicine chiefly as a nervous system stimulant. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: caffeine (Thesaurus) caffeinated caffeinism Related Content Daily Word Quiz: dormant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language